Generally, there is known an electric stapler in which a sheet staple constituted by connecting a number of staples in a straight form in a sheet-like shape is contained in a staple cartridge, the staple cartridge is inserted and detached into and from a path for mounting the cartridge formed at a magazine portion of a stapler main body, the staple cartridge is inserted to attach thereto and thereafter, both sides of a staple are successively folded to bend to strike out from a staple at a front portion of the sheet staple. According to such a system of an electric stapler, when a remaining amount of the sheet staple in the staple cartridge expires, the cartridge needs to be drawn out from the magazine portion to interchange by a new one thereof. For such a purpose, it is necessary to provide a staple detecting sensor for detecting the remaining amount of the sheet staple at inside of the staple cartridge in the staple main body, or interchange a refill at inside of the cartridge.
However, a remaining amount detecting sensor of a background art is provided at the stapler main body for detecting whether a sheet-like staple is present at inside of the staple cartridge as indicted in FIG. 2 of JP-Y-07-30282 by notation 41. Therefore, although presence or absence of the sheet-like staple can be detected, a degree of a remaining amount of to what degree the remaining amount is reduced cannot be known. Therefore, even when the remaining amount is small, a result of detection indicates as ‘present’ and when an electric stapler is provided to a copier or a printer, an operator is not informed of an accurate remaining amount.